For Internet communication, TCP (Transport Control Protocol) being a communication system (protocol) using a logical communication channel is generally used. The TCP has some communication control functions in order to perform reliable data communication. The functions include three-way handshake to start data transmission after checking communication destination, a congestion control function to prevent congestion on a physical communication channel, and a retransmission function in the case where packet loss occurs. Furthermore, there is also an arrangement called slow starting to prevent a large quantity of traffic from suddenly flowing into a network. However, at the present time of increased transmission rates and wide variety of communications systems, there is also situations where functions such as the three-way handshake and the slow starting become overhead, and in this case, high-speed communication may be obstructed.
In contrast, in wireless LANs (Local Area Networks), which in recent years, have been rapidly in widespread use, it is known that transmission rates are high at locations close to a wireless LAN access point, whereas transmission rates become low at distant locations. That is, even in one network, it becomes a common case where transmission rates or communication qualities vary according to positions. It is desired to perform effectively communication using the TCP even in such an environment where transmission rates or communication qualities vary within such an identical network.